Catalytic performance of vanadium pyrophosphate oxides (VPO) in the oxidative dehydration of glycerol

A series of vanadium pyrophosphate oxide catalysts were prepared by thermally treating catalyst precursor VOHPO4 center dot 0.5H(2)O in the temperature range of 500-900 degrees C in nitrogen and their catalytic activities were evaluated in glycerol dehydration with molecular oxygen. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric-differential thermal analysis and temperature programmed desorption of ammonia. The dehydration activity depends on treatment temperature on the catalyst precursor: the catalyst treated at 800 degrees C exhibits the best result with 100% glycerol conversion and more than 95% selectivity for useful products, including acrolein (64%), acetaldehyde, acetic acid and hydroxyacetone. We observed that the addition of molecular oxygen into reaction could greatly reduce the selectivity for by-products from 20% to 4% and can avoid coke formation. The dehydration activities of the catalysts were correlated with the characteristics of the catalysts. (C) 2009 Elsevier B.V. All rights reserved.